thinkphp自定义业务逻辑有有关问题

thinkphp自定义业务逻辑有问题?
模型:

PHP code

class DepartmentModel extends Model{
    
    public function getIndexDepart()
    {
        return 1; 
    }
      

PHP code

 
 class IndexAction extends Action 
 { 
     public function index() 
     { 
 		$a = D('Department'); 
 		echo " 
"; 
 		print_r($a->getIndexDepart()); 
 		echo " 
"; 
         //echo THINK_PATH; 
     } 

 } 

PHP code

class IndexAction extends Action
{
    public function index()
    {
        $a = D('Department');
[color=#FF0000]        get_class($a);[/color]
        echo "
";
        print_r($a->getIndexDepart());
        echo "
";
        //echo THINK_PATH;
    }

}